• T336B Circuit Test Set
• T279 Circuit Termination Set
• T136B Circuit Test Set
• T318B Line Access Set

• T304B/T305 Bond Current Meter/Current Probe
• T124 Cable Shield Splice Tester
• T207 Longitudinal Balance Test Set
• T240 Artificial Cable Kits

The T336B Circuit Test Set is a compact, tough, light-weight, portable, battery powered test set designed to evaluate and trouble-shoot telecommunications circuits. The T336B complements and adds to the capabilities of the time tested and proven T136 Series of Circuit Test Sets. The T136’s are used by installation, repair, and cable maintenance personnel in all the major telephone operating companies of the United States. Additional features and measuring capabilities have been added to the T336B. These features, combined with the features of the T136 Series Circuit Test Set, result in a very versatile test set for general purpose testing by telephone operating companies, specialized common carriers, inter-connect companies and large telecommunications users.

Features added to the T336B include auto-ranging of level and noise measurements, permitting easier use and increased overall ranges. Also added are provisions for DC resistance measurement. Ranges and impedances are designed to conform the the AT & T requirements for subscriber loop transmission test sets.

The Model T279 provides the termination and balance arrangements required for sectionalizing noise measurements on a circuit. It is designed to facilitate noise investigations by installers and repairmen. When it is necessary to make noise measurements on sections of a circuit to identify the section which may be introducing the noise, it is necessary to provide the proper termination of the section under test with an appropriate terminating resistor and a well balanced center tapped coil to provide means for maintaining the longitudinal circuit. The balance of the coil must be such that it will not contribute any unbalance to the circuit under test.

The Model T279 includes a balanced center tapped coil, a terminating resistor, two pairs of clip leads labeled FIELD and CO, and binding post terminals labeled TO MEAS SET. A toggle switch selects the direction in which measurement is to be made, either toward CO or toward FIELD, as shown on the front panel schematic illustration. The balance coil is connected across the line in the direction of measurement, while the line in the opposite direction is shorted and connected to the coil center tap to maintain the longitudinal path. A binding post terminal labeled G provides a means for making an external connection to the coil center tap. This terminal should be left unconnected during most measurements.

The Model T136B Circuit Test Set is designed for use by the installers and repairmen in conducting circuit transmission and noise measurements without using elaborate or expensive equipment. It allows for simple, easily read loop parameter measurements. The T136 provides a 600 W AC impedance and a 430 W DC impedance across Tip and Ring, insuring a precise termination for performance testing. These impedances are in compliance with EIA specification RS470.

All operating functions are selected via single six position rotary switch. DIAL position allows for the external connection of a remote telephone handset directly to the line, by connecting to the square Dial Posts. Three four-foot long leads equipped with clips and colored green for Tip, red for Ring and yellow for Ground are permanently attached to the set.

A nonlocking pushbutton switch is used to supply power to the measuring circuits from two small 9 volt batteries. No current is supplied by the batteries until the switch is pressed to take a reading. Consequently, the useful life of the batteries can approach shelf life because the ON period is usually very short.

On the T136BSBZW version, the scale is divided into two colored sections, red from 0 mA to 23 mA and green from 23 mA to 100 mA. On the T136BGMZW version, a yellow section is included from 20 mA to 23 mA.

The Model T318B Line Access Set provides access to 2-wire and 4-wire facilities. Whether used by telephone companies, common carriers, or private networks. The Model T318B enables quick and efficient interfacing of analog transmission facilities. This unit is particularly useful at the network demarcation point where it is used to simulate network functions towards the customer-owned equipment, or to simulate the customer-owned equipment functions towards the network.

Trunks and lines to PBX's, Automatic Call Distributor's, Key Systems, and Secretarial Answering Systems are accessed from the serving central office or at the network demarcation point. The T318B provides the interface connections required for testing equipment for noise, transmission, signaling and supervision testing on the transmission facility.

The Model T318B Line Access Set is powered by ac line voltage. It is housed in a rugged, sturdy, metal case and is designed to withstand the severe conditions that may be encountered in field applications. All the features required to seize, supervise, signal and control both 2-wire and 4-wire facilities are built-in, easily accessible and quickly mastered. The Model T318B resolves the access dilemma at the demarcation point.

The T304 and T304B Current Meters are light weight, rugged, easy to use test sets that are designed to measure alternating currents from 10 mA to 100 A. When used with either a T305 or T272A Current Probe, the T304 and T304B will measure cable shield currents without disrupting or disconnecting cable shield connections. The T304B's bond checking feature allows immediate on-site bond condition assessments to be made.

Model T304
The T304 Current Meter is a battery powered test set designed to display the output of the T305 and T272A Current Probes. These probes connect to the T304 through dual banana jack connectors. The T304 features a seven position switch selecting current ranges of 100mA, 300mA, 1A, 3A, 10A, 30A and 100A. A battery test button allows instantaneous display of battery status. In addition to an on/off switch, which is mechanically forced to the off position when the cover is closed, a switch selects use of either the T305 or T272 probes. The T304 is powered by two 9 V standard transistor radio batteries which will provide approximately 300 hours of normal (intermittent) operation.

Model T304B
The T304B has all the features and controls of the T304. In addition, the T304B allows rapid and accurate evaluation of any cable shield bond or connection, analyzing whether or not they are defective. A current induced upon the cable shield is used to evaluate the bond state. For those instances where such induced currents are either too low or are non-existent, the T304B has a built-in current source which will supply local current through the shield connections to allow the bond check to be made.

Model T305
The T305 Current Probe is a clamp-on current transducer. It is hinged to open, allowing conductors or cables up to approximately two inches in diameter to be measured. A five foot cord with a dual banana plug allows connection to either the T304 or T304B. The T305/T272 Selector Switch on the T304 and T304B should be in the T305 position when this probe is used.

Model T272A
The T272A Current Probe is a clamp-on current transducer which allows cables and conductors up to 4 inch overall diameter to be measured. It can be used with the T304 or T304B. The probe selector switch on the T304 or T304B should be set to T305 when using the T-272A.

The Model T124 Cable Shield Splice Continuity Tester is an accurate measuring device which provides measurement of the conditions existing at cable shield splices, checks the integrity of ground connection, and checks the condition of capacitors across insulated splices. Two probes, capacitively coupled to the shield of the cable under test, are connected to very high-input impedance amplifiers contained in the probe assemblies. The outputs of the two amplifiers are fed through a cable to a balanced transformer circuit in a measuring set. The measuring set is connected to any stable ground.

A key switch is provided to permit measurement of the voltage to ground picked up by each probe. The two voltages should be equal if the splice is good, and different if the splice is defective. This feature makes the set useful for identifying the nature of a variety of faults in splices, and also for checking ground connections.

The Model T207 Longitudinal Balance Test Set is designed to measure the longitudinal balance of single-port or two-port circuits and devices. This test set permits evaluation of relays, feed coils, networks, long-line units, amplifiers and other equipment present on the typical communications circuit. These devices may have poor longitudinal balance and thus contribute to the susceptibleness of the facility. The measuring technique and circuit configuration conforms to the IEEE standard 455-1976 for Longitudinal Balance Measurements.

Longitudinal balance measurements may be made at single frequencies in the range of 40 Hz to 4 kHz. Also, as an added feature of the Model T207, a figure of merit balance measurement may be made using a shaped waveform which is representative of a power induced noise spectral distribution. Single frequency measurements on circuits with balance approaching 80 dB can be made with a typical accuracy of ± 1 dB.

A source of DC current is provided for the device under test to facilitate the simulation of actual operating conditions.

The Model T240 is an advanced concept in artificial cable kit design providing line sections which closely represent actual telephone cable sections, and including facilities which simplify and expedite the analysis of fault conditions on a cable when used in conjunction with the T195 Level Tracer. Switches are included for introducing conditions which normally would require the removal of modules from an artificial line and then reassembling the line.

New features make it possible to set up conditions for analyzing the effects of split pairs, unbalanced grounded ringers, high series resistance unbalance, shunt capacitance unbalance, bridged taps, and the effect of missing or improperly connected load coils, and to estimate how many bridged ringers may be on a loop. Appropriate precision and compromise networks are provided for return loss and impedance measurements. All modules are enclosed in 2" X 2" X 3/4" aluminum cans and equipped with rugged connectors for insertion and receptacles on a plug-board panel.

The basic package consists of a plugboard unit and cover. The plugboard is equipped with receptacles for mounting the plug-in line sections and load coil modules. The accessory cover has a panel which provides a variety of switchable conditions and a storage area for patch cords. An optional plain cover is available which provides storage for 96 plug-in modules.